FCPX share to blu-ray

I have obviously made a tragic mistake but can not see where and would appreciate some
I import video from an AX2000 to my iMac (2.7 GHz Intel OS-10.9.1) and edit in FCPX 10.1 ending with a 54 min movie.
I share to Blu-ray (H.264 .. etc) and select the Samsung SE 506 as the destination burner (it appears in the drop down menu along with the installed DVD burner).
The computer grinds for 3-4 hours then asks me to insert a blank BD (25GB TDK) disk - which I do - and that the process is 86% complete.
The burner starts burning and does so all night long and finally I disconnect the USB from the computer as it is still at 86% complete,the same % as when I went to bed.
The BD disk has a small section burnt - about 1/4 inch - which is unplayable.
I would really appreciate some advice as to where my error lies?
Thanks
David
(I am posting this on 26th; however, I can not reply to any questions until the 31/12/13 (I am travelling to an internet-free-zone from 27-31 Dec to record some Australian country life) so I shall look to answer any questions as soon as I return.

Probably, no error on your part at all. It could have been a faulty disc, or a on-of-those-things glitch in the process. Personally, I always create a DVD / BD image and use something like Toast to burn it as I get better feedback about the progress.